Blood serum glycoproteins isolated from antarctic fishes are being used to investigate the nature of freezing damage which occurs when red blood cells, spermatozoa and tissues are subjected to subzero temperatures. One of the theories proposed to explain freezing damage states that cellular damage results from exposure to the high salt concentrations which occur during the freezing process. We have recently shown that in the presence of glycoprotein antifreezes salts are not concentrated during freezing. Despite this unusual property spermatozoa are not protected by the glycoproteins during freezing and in fact they suffer more freezing damage than if no cryoprotective agent were added. This interesting finding indicates a specific binding must occur between the gycoproteins and human spermatozoa making it more labile to freezing. Such findings suggest to us that prevention of salt concentration during freezing is not one of the primary causes of freezing damage.